U.S. patent application number 15/710327 was filed with the patent office on 2018-03-29 for electrostatic charge image developing white toner, manufacturing method thereof, image forming apparatus, and image forming method.
The applicant listed for this patent is Konica Minolta, Inc.. Invention is credited to Atsushi IIOKA, Kouji IZAWA, Takanari KAYAMORI, Masaharu MATSUBARA, Naoya TONEGAWA.
Application Number | 20180088481 15/710327 |
Document ID | / |
Family ID | 59997269 |
Filed Date | 2018-03-29 |
United States Patent
Application |
20180088481 |
Kind Code |
A1 |
KAYAMORI; Takanari ; et
al. |
March 29, 2018 |
ELECTROSTATIC CHARGE IMAGE DEVELOPING WHITE TONER, MANUFACTURING
METHOD THEREOF, IMAGE FORMING APPARATUS, AND IMAGE FORMING
METHOD
Abstract
An electrostatic charge image developing white toner according
to the present invention includes toner base particles including
rutile type titanium oxide particles as colorant and a binder
resin. The rutile type titanium oxide particles are composed of two
groups Ga and Gb of rutile type titanium oxide particles have
different volume particle size distribution. A volume particle size
distribution curve of the rutile type titanium oxide particles
represents diameter on a horizontal axis and volume ratio on a
vertical axis and has two main peaks. Diameters Da and Db of peak
top positions of the two main peaks are respectively within a range
of 100 to 500 nm, and satisfy following Relational expressions: 25
nm.ltoreq.Db-Da.ltoreq.200 nm (Relational expression 1): (mass of
Ga):(mass of Gb)=5:95 to 30:70 (Relational expression 2):
Inventors: |
KAYAMORI; Takanari;
(Kawasaki-shi, JP) ; MATSUBARA; Masaharu; (Tokyo,
JP) ; TONEGAWA; Naoya; (Sagamihara-shi, JP) ;
IZAWA; Kouji; (Tokyo, JP) ; IIOKA; Atsushi;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Konica Minolta, Inc. |
Tokyo |
|
JP |
|
|
Family ID: |
59997269 |
Appl. No.: |
15/710327 |
Filed: |
September 20, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G 9/08782 20130101;
G03G 9/0806 20130101; G03G 9/0819 20130101; G03G 9/0926 20130101;
G03G 9/0902 20130101; G03G 9/09725 20130101; G03G 9/0832 20130101;
G03G 9/08755 20130101; G03G 9/08722 20130101; G03G 9/0827 20130101;
G03G 9/0833 20130101; G03G 9/09716 20130101; G03G 9/0823
20130101 |
International
Class: |
G03G 9/097 20060101
G03G009/097; G03G 9/08 20060101 G03G009/08; G03G 9/083 20060101
G03G009/083 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2016 |
JP |
2016-190868 |
Claims
1. An electrostatic charge image developing white toner comprising
toner base particles comprising rutile type titanium oxide
particles as colorant and a binder resin, wherein the rutile type
titanium oxide particles are composed of two groups Ga and Gb of
rutile type titanium oxide particles having different volume
particle size distribution, and a volume particle size distribution
curve of the rutile type titanium oxide particles represents
diameter on a horizontal axis and volume ratio on a vertical axis
and has two main peaks, wherein diameters Da and Db of peak top
positions of the two main peaks are respectively within a range of
100 to 500 nm, and satisfy following Relational expressions: 25
nm.ltoreq.Db-Da.ltoreq.200 nm (Relational expression 1): (mass of
Ga):(mass of Gb)=5:95 to 30:70 (Relational expression 2):
2. The electrostatic charge image developing white toner according
to claim 1, wherein total mass of the two groups Ga and Gb of
rutile type titanium oxide particles are within a range of 20 to 60
mass % relative to 100 mass % of the binder resin.
3. The electrostatic charge image developing white toner according
to claim 1, wherein the diameters Da and Db are respectively within
a range of 200 to 300 nm.
4. The electrostatic charge image developing white toner according
to claim 1, wherein the diameters Da and Db satisfy following
Relational expression 3: 20 nm.ltoreq.Db-Da.ltoreq.100 nm
(Relational expression 3):
5. The electrostatic charge image developing white toner according
to claim 1, comprising a vinyl resin as the binder resin.
6. A manufacturing method to manufacture the electrostatic charge
image developing white toner according to claim 1, comprising a
step of preparing a dispersion liquid of the binder resin, a
dispersion liquid of the group Ga of rutile type titanium oxide
particles, and a dispersion liquid of the group Gb of rutile type
titanium oxide particles; and a step of aggregating and fusing the
binder resin, the group Ga of rutile type titanium oxide particles,
and the group Gb of rutile type titanium oxide particles.
7. An image forming apparatus comprising a charger, an
electrostatic charge image former, a developer, a transferring
unit, and a fixer, wherein the developer forms a toner image by
developing an electrostatic charge image using a developing agent
for electrostatic charge image development comprising the
electrostatic charge image developing white toner according to
claim 1.
8. The image forming apparatus according to claim 7, comprising
five or more electrostatic charge image formers and five or more
developers.
9. An image forming method comprising forming a latent image,
developing, transferring, and fixing; using the electrostatic
charge image developing white toner according to claim 1 and an
electrostatic charge image developing colored toner comprising
colorant exhibiting a color other than white.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Japanese Patent Application No. 2016-190868 filed on Sep.
29, 2016 including the description, claims, drawings, and abstract
the entire disclosure is incorporated by reference in its
entirety.
BACKGROUND
Technological Field
[0002] The present invention relates to an electrostatic charge
image developing white toner, a manufacturing method thereof, an
image forming apparatus, and an image forming method. More
specifically, the present invention relates to an electrostatic
charge image developing white toner and the like having hiding
property, hue, and transfer property and complying with the demand
in the market of production printing.
Description of the Related Art
[0003] With the recent spread of application of electrophotographic
technology, the demand for enhancing expressiveness is enhanced,
for example, by color printing not only on white paper but on
colored paper, by printing on a film, a transparent sheet such as
OHP sheet, and a label. An electrostatic charge image developing
white toner (hereinafter also referred to as "white toner" or
simply as "toner") may be used as an undercoat for clear color
development in printing on such medium or as an overcoat which
functions as an light reflection layer on a reverse image formed on
the film.
[0004] White toner image requires excellent hiding property in
order to sufficiently function as an undercoat layer. Here, the
hiding property means the invisibility of the reverse side from the
front side through the white toner image. In order to obtain
completely white toner image, all the incident light on the white
toner image is required to be scattered and reflected.
[0005] For example, Japanese Patent Application Laid-Open
Publication No. 2013-109097 discloses a technique to suppress the
aggregation of titanium oxide particles by adding a certain amount
of titanium oxide particles having specific diameter and thereby to
improve the scattering property of titanium oxide particles in the
mixture of toner materials. According to the technique of Japanese
Patent Application Laid-Open Publication No. 2013-109097, the
titanium oxide particles uniformly scattered in a toner particle
makes uniform thermal conductivity and suppresses local overheating
in the toner particle, and thereby improves high-temperature offset
resistivity, prevents local leak of charge, and suppresses transfer
omission.
[0006] Japanese Patent Application Laid-Open Publication No.
2012-154957 discloses specifying the ratio of rutile type titanium
oxide and anatase type titanium oxide to provide a toner that can
suppress reduced image storage performance due to
discoloration.
[0007] Japanese Patent Application Laid-Open Publication No.
2012-128008 discloses a toner containing a binder resin and at
least two or more white pigments, which includes a porous titanium
oxide in order to adjust hue.
[0008] However, whiteness (hiding property), hue, and transfer
property are not sufficient according to the white toner described
in Japanese Patent Application Laid-Open Publication Nos.
2013-109097, 2012-154957, or 2012-128008. They cannot accelerate
image formation or enhance the image quality of obtained visible
images to comply with the demand in the market of production
printing.
SUMMARY
[0009] An object of the present invention, which has been
accomplished to solve the problem described above, is to provide an
electrostatic charge image developing white toner and the like
having hiding property, hue, and transferability complying with the
demand in the market of production printing.
[0010] The present inventors have examined the causes of the above
mentioned problems in order to solve the above problems and arrived
at the present invention on the basis of the finding that white
toner having good hiding property, hue, and transfer property can
be provided by using two groups of rutile type titanium oxide
particles, when a volume particle size distribution is different
from each other and satisfies specific relations.
[0011] To achieve at least one of the above-mentioned objects,
according to an aspect of the present invention, an electrostatic
charge image developing white toner includes a toner base particles
including rutile type titanium oxide particles as colorant and a
binder resin, wherein
[0012] the rutile type titanium oxide particles are composed of two
groups Ga and Gb of rutile type titanium oxide particles having
different volume particle size distribution, and
[0013] a volume particle size distribution curve of the rutile type
titanium oxide particles represents diameter on a horizontal axis
and volume ratio on a vertical axis and has two main peaks, wherein
diameters Da and Db of peak top positions of the two main peaks are
respectively within a range of 100 to 500 nm, and satisfy the
following Relational expressions:
25 nm.ltoreq.Db-Da.ltoreq.200 nm (Relational expression 1):
(mass of Ga):(mass of Gb)=5:95 to 30:70 (Relational expression
2):
[0014] According to another aspect of the present invention, a
manufacturing method of the electrostatic charge image developing
white toner includes:
[0015] a step of preparing a dispersion liquid of the binder resin,
a dispersion liquid of the group Ga of rutile type titanium oxide
particles, and a dispersion liquid of the group Gb of rutile type
titanium oxide particles; and
[0016] a step of aggregating and fusing the hinder resin, the group
Ga of rutile type titanium oxide particles, and the group Gb of
rutile type titanium oxide particles.
[0017] According to another aspect of the present invention, an
image forming apparatus includes a charger, an electrostatic charge
image former, a developer, a transferring unit, and a fixer,
wherein
[0018] the developer forms a toner image by developing an
electrostatic charge image using a developing agent for
electrostatic charge image development including the electrostatic
charge image developing white toner according to the present
invention.
[0019] According to another aspect of the present invention, an
image forming method includes forming a latent image; developing;
transferring; fixing; and
[0020] uses the electrostatic charge image developing white toner
according to the present invention and an electrostatic charge
image developing colored toner including colorant exhibiting a
color other than white.
BRIEF DESCRIPTION OF THE DRAWING
[0021] The advantages and features provided by one or more
embodiments of the invention will become more fully understand from
the detailed description given hereinbelow and the appended
drawings which are given by way of illustration only, and thus are
not intended as a definition of the limits of the present
invention:
[0022] FIG. 1 is a schematic diagram of an exemplary volume
particle size distribution curve of rutile type titanium oxide
particle according to the present invention.
[0023] FIG. 2 is a schematic cross section diagram of an exemplary
image forming apparatus according to the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0024] Hereinafter, one or more embodiments of the present
invention will be described with reference to the drawings.
However, the scope of the invention is not limited to the disclosed
embodiments.
[0025] Two kinds of titanium oxide used are mainly known as a white
pigment, one having a rutile type crystalline structure and another
having an anatase type crystalline structure titanium oxide. The
rutile type titanium oxide has higher refractive index than the
anatase type titanium oxide. Higher refractive provides higher
hiding power by enhancing efficiency of reflecting and scattering
light at the interface of the resin and the titanium oxide.
Furthermore, the rutile type titanium oxide has less oxidation
effect as a photocatalyst and results in less chalking and
excellent light resistance.
[0026] For obtaining high hiding power, the rutile type titanium
oxide particles (hereinafter, simply referred to as "titanium oxide
particles") preferably have a diameter that provides the maximum
light scattering property of visible light. Specifically, the main
peaks of the volume particle size distribution curve (horizontal
axis: particle diameter, vertical axis: volume ratio) of the rutile
type titanium oxide particles have peak tops at a position
corresponding to diameters within the range of 100 to 500 nm, more
preferably 200 to 300 nm. The shape of the titanium oxide particles
may be spherical shape, needle shape, spindle shape, and the like.
In the present invention, spherical shape is preferred from the
viewpoint of improving hiding rate.
[0027] Furthermore, it is necessary to increase the mass of the
titanium oxide contained in the toner base particles for improving
hiding power.
[0028] When mass (content) of the titanium oxide particles
contained in the toner base particles is small, titanium oxide
particles having a smaller diameter improves higher hiding power
because of the large surface area for scattering light.
[0029] However, as the content of titanium oxide particles having a
small diameter is increased, hiding power starts to be reduced
(crowding effect) at a certain level. Titanium oxide particles
having a small diameter easily cause the crowding effect and
largely reduce the hiding power. The hiding power starts to be
improved again when the content is larger than the level that
causes the crowding effect. Titanium oxide particles having a large
diameter with small crowding effect can provide larger hiding power
compared to those having a small diameter when the content (mass)
is very large. However, the resistance and transfer property of the
toner are reduced by filling only the titanium oxide particles
having a large diameter with high concentration. The titanium oxide
particles having a large diameter cannot function effectively when
content is too small. According to the present invention, the
transfer property is considered to be improved by using two groups
of titanium oxide particles having different diameters in
combination.
[0030] The present inventors considered that, by using two groups
of titanium oxide particles having different diameters in
combination, the content can be adjusted to the value at which the
hiding power is the maximum without causing the crowding effect. It
is considered that the hiding power can be improved with lower
parts of titanium oxide according to the present invention compared
to the case in which one group of titanium oxide particles are
densely filled.
[0031] As a result of intensive studies, the present inventors
arrived at the present invention based on the finding that when the
diameters of the peak-top position of the two main peaks are
respectively referred to as Da and Db in a volume particle size
distribution curve of the two groups of rutile type titanium oxide
particles, it is preferred that the Da and Db are respectively
within the range of 100 to 500 am and satisfy the following
Relational expressions:
25 nm.ltoreq.Db-Da.ltoreq.200 nm (Diameter difference: Relational
expression 1):
(mass of Ga):(mass of Gb)=5:95 to 30:70 (Filling ratio: Relational
expression 2):
[0032] Because the rutile type titanium oxide highly absorbs light
at a wavelength of near 400 nm and slightly tinged in yellow, a
complementary color, the hue of the rutile type titanium oxide is
slightly yellowish compared to that of the anatase type titanium
oxide. Meanwhile, the hue becomes bluish as the volume average
particle diameter becomes small. According to the present
invention, the hue can also be improved by adding smaller titanium
oxide particles having Da and Db within the range of 100 to 500
nm.
[0033] The electrostatic charge image developing white toner
according to the present invention includes toner base particles
including rutile type titanium oxide particles as colorant and a
binder resin. The rutile type titanium oxide particles are composed
of two groups (Ga and Gb) of rutile type titanium oxide particles
having different volume particle size distribution. A volume
particle size distribution curve (horizontal axis: diameter,
vertical axis: volume ratio) of the rutile type titanium oxide
particles has two main peaks. The diameters Da and Db of peak top
positions of the two main peaks are respectively within the range
of 100 to 500 nm and satisfy the above Relational expression 1 and
Relational expression 2. They are technical features common to or
corresponding to the present invention. According to these
technical features, the present invention can provide an
electrostatic charge image developing white toner and the like
having hiding property, hue, and transfer property complying with
the demand in the market of production printing.
[0034] In a preferred embodiment of the present invention, total
mass of the two groups (Ga and Gb) of rutile type titanium oxide
particles are within a range of 20 to 60 mass % relative to 100
mass % of the binder resin. Hiding property, hue, and transfer
property can be thereby improved.
[0035] In another preferred embodiment of the present invention,
the diameters Da and Db of the peak top position are respectively
within the range of 200 to 300 nm. Hiding property, hue, and
transfer property can be thereby improved.
[0036] In another preferred embodiment of the present invention,
the diameters Da and Db of the peak top positions satisfy the
following Relational expression 3. Hiding property, hue, and
transfer property can be thereby improved.
20 nm.ltoreq.Db-Da.ltoreq.100 nm (Relational expression 3):
[0037] In another preferred embodiment of the present invention, a
vinyl resin is included as the binder resin. Transfer property can
be thereby improved.
[0038] In a preferred embodiment of the present invention, a
manufacturing method of the electrostatic charge image developing
white toner according to the present invention includes the
following steps. A step of preparing a dispersion liquid of the
binder resin, a dispersion liquid of the group Ga of rutile type
titanium oxide particles, and a dispersion liquid of the group Gb
of rutile type titanium oxide particles, and a step of aggregating
and fusing the binder resin, the group Ga of rutile type titanium
oxide particles, and the group Gb of rutile type titanium oxide
particles. An electrostatic charge image developing white toner
having good hiding property, hue, and transfer property can be
thereby manufactured.
[0039] In a preferred embodiment of the present invention, an image
forming apparatus using the electrostatic charge image developing
white toner according to the present invention includes a charger,
an electrostatic charge image former, a developer, a transferring
unit, and a fixer. The developer preferably forms a toner image by
developing an electrostatic charge image using a developing agent
for electrostatic charge image development including the
electrostatic charge image developing white toner according to the
present invention. An image having good hiding property, hue, and
transfer property can be thereby formed.
[0040] In another preferred embodiment of the present invention, an
image forming apparatus using the electrostatic charge image
developing white toner according to the present invention includes
five or more electrostatic charge image formers and five or more
developers. A full color image can be thereby formed with white
color having hiding property, hue, and transfer property that
comply with the demand in the market of production printing.
[0041] In a preferred embodiment of the present invention, the
image forming method using the electrostatic charge image
developing white toner according to the present invention includes
forming a latent image, developing, transferring, and fixing. In
the embodiment, the electrostatic charge image developing white
toner according to the present invention and an electrostatic
charge image developing colored toner including colorant exhibiting
a color other than white are preferably used. A method for forming
a color image having good hiding property, hue, and transfer
property can be thereby provided.
[0042] The present invention and its constituent and embodiments
for achieving the present invention will now be described in
detail. Throughout the specification, "to" between two numerical
values indicates that the lower limit includes the numeric value
before "to" and that the upper limit includes the numeric value
after "to".
<<Summary of Electrostatic Charge Image Developing White
Toner>>
[0043] The electrostatic charge image developing white toner
according to the present invention includes toner base particles
including rutile type titanium oxide particles as colorant and a
binder resin. The rutile type titanium oxide particles are composed
of two groups (Ga and Gb) of rutile type titanium oxide particles
having different volume particle size distribution. The volume
particle size distribution curve (horizontal axis: particle
diameter, vertical axis: volume ratio) of the rutile type titanium
oxide particles have two main peaks, and the diameters Da and Db of
the peak top positions of the two main peaks are respectively
within the range of 100 to 500 nm and satisfy the above Relational
expression 1 and Relational expression 2.
[0044] A "toner" means an assembly of "toner particles" in the
present invention.
[Toner Base Particle]
[0045] The toner base particles according to the present invention
include rutile type titanium oxide particles as colorant and a
binder resin.
[0046] The toner base particles according to the present invention
can be used as toner particles as they are, however, the toner base
particles with an external additive are preferably used as toner
particles.
[Colorant]
[0047] The toner base particles according to the present invention
include rutile type titanium oxide particles as colorant.
<Rutile Type Titanium Oxide Particle>
[0048] The rutile type titanium oxide (hereinafter, also simply
referred to as "titanium oxide") particles are composed of two
groups (Ga and Gb) of rutile type titanium oxide particles having
different volume particle size distribution from each other. The
volume particle size distribution curve (horizontal axis: diameter,
vertical axis: volume ratio) of the rutile type titanium oxide
particles has two main peaks. The diameters (Da and Db) of the peak
top positions of the two main peaks are respectively within the
range of 100 to 500 nm and satisfy the following Relational
expressions 1 and 2:
25 nm.ltoreq.Db-Da.ltoreq.200 nm (Relational expression 1):
(mass of Ga):(mass of Gb)=5:95 to 30:70 (Relational expression
2):
[0049] Preferably, in the volume particle size distribution curve
of the rutile type titanium oxide particle, Da and Db (diameters of
peak top positions of two main peaks in volume particle size
distribution curve) are respectively within the range of 200 to 300
nm from the viewpoint of improving hiding property, hue, and
transfer property.
[0050] Preferably, total mass of the two groups (Ga and Gb) of
rutile type titanium oxide particles are within a range of 20 to 60
mass % relative to 100 mass % of the binder resin, from the
viewpoint of improving hiding property, hue, and transfer
property.
[0051] Preferably, Da and Db (diameters of peak top positions of
two main peaks in volume particle size distribution curve) satisfy
the following Relational expression 3, from the viewpoint of
improving hiding property, hue, and transfer property.
20 nm.ltoreq.Db-Da.ltoreq.100 nm (Relational expression 3):
[0052] When the two groups of the rutile type titanium oxide
particles are almost equivalent in content, the diameter range
which causes crowding effect can be prevented from overlapping by
making the diameters Da and Db of the peak top position
respectively within the range of 100 to 500 nm and (Da-Db) 25 nm or
more. As a result, reduction in hiding rate can be suppressed.
Furthermore, when (Da-Db) is 100 nm or less, reduction in hiding
rate due to crowding effect can be further suppressed and the
titanium oxide particles can be uniformly captured in the toner
resin. As a result, transfer property is further improved.
[0053] The rutile type titanium oxide is prepared using ilmenite as
a starting material. Meta-titanic acid slurry is prepared by
hydrolysis of the dispersion liquid obtained by decomposition of
ilmenite with sulfuric acid. After adjusting the pH of the
meta-titanic acid slurry, titanium oxide is obtained by filtration,
calcination, and crushing. The obtained titanium oxide is dispersed
in a solution and mixed and reacted with hydrophobic agent added
dropwise. The rutile type titanium oxide is obtained by filtration,
calcination, and crushing of the solution.
[0054] The volume particle size distribution curve of the rutile
type titanium oxide particle represents diameter on a horizontal
axis and volume ratio on a vertical axis and is prepared on the
basis of the primary diameter of randomly-selected 100 particles
measured with a transmission type electron microscope. In the
volume particle size distribution curve, the maximum point of the
peak is determined as a "peak top". Primary diameter does not refer
to the diameter of the aggregate but the diameter of a particle
which is not aggregated.
[0055] The "main peaks" according to the present invention refer to
the peaks having the first and the second maximum intensity (value
of the vertical axis) among the peaks within 100 run to 500 nm in
the obtained volume particle size distribution curve.
[0056] The volume particle size distribution curve of the titanium
oxide particles included in a manufactured toner can be prepared by
the same measurement method described above, by extracting the
titanium oxide particles through elution of toner resin from
tetrahydrofuran (THF). When there are two main peaks of diameter as
in FIG. 1, two groups (Ga and Gb) of rutile type titanium oxide
particles are determined by separation with the border line (B)
between the main peaks. The area ratio of Ga and Gb is thereby
calculated. The border line is determined by the diameter
corresponding to the minimum intensity (value of the vertical axis)
between the main peaks. The area ratio of Ga and Gb can be
converted into volume ratio of Ga and Gb. Because volume is
proportional to and can be converted into mass using specific
gravity, the volume ratio of Ga and Gb corresponds to the mass
ratio of Ga and Gb. Accordingly, the mass ratio of Ga and Gb
described in Relational expression 2 can be calculated from a
manufactured toner.
[0057] The crystal structure of the titanium oxide in the toner can
be observed using raman spectroscopic apparatus.
[0058] In the present embodiment, the titanium oxide particles may
be used after modifying the surface with other compound
(hereinafter may be referred to as "surface modification"). Surface
modification includes modifying the surface with oxide hydrate of
Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, and the like, and doping a
small amount of different metal such as Al and Zn on the titanium
oxide crystal lattice. Furthermore, the surface-modified titanium
oxide may be treated with a coupling agent and the like.
[0059] Surface modifier is not particularly limited, and examples
of surface modifier include silane coupling agent. Surface modifier
may be used alone or in combination of two or more. Surface
modification can be performed, for example, by immersion of the
titanium oxide particles to the surface modifier.
[0060] Examples of the silane coupling agent include special
silylating agents. More specific examples of the silane coupling
agent include methyltrichlorosilane, dimethyldichlorosilane,
trimethylchlorosilane, phenyltrichlorosilane,
diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane,
dimethyldimethoxysilane, phenyltrimethoxysilane,
diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane,
dimethyldiethoxysilane, phenyltriethoxysilane,
diphenyldiethoxysilane, isobutyltrimethoxysilane,
decyltrimethoxysilane, hexamethyldisilazane, N,O-(bis
trimethylsilyl) acetamide, N,N-(trimethylsilyl)urea,
tert-butyldimethylchlorosilane, vinyltrichlorosilane,
vinyltrimethoxysilane, vinyltriethoxysilane,
.gamma.-methacryloxypropyltrimethoxysilane,
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
.gamma.-glycidoxypropyltrimethoxysilane,
.gamma.-glycidoxypropylmethyldiethoxysilane,
.gamma.-mercaptopropyltrimethoxysilane, and
.gamma.-chloropropyltrimethoxysilane.
[0061] Within a range not inhibiting the advantageous effects may
be used inorganic pigments (heavy calcium carbonate, light calcium
carbonate, titanium dioxide, aluminum hydroxide, satin white, talc,
calcium sulfate, barium sulfate, zinc oxide, magnesium oxide,
magnesium carbonate, amorphous silica, colloidal silica, white
carbon, kaolin, calcined kaolin, delaminated kaolin,
aluminosilicate, sericite, bentonite, smectite, etc.); organic
pigments (polystyrene resin particles, urea formalin resin
particles, etc.); and pigments having a hollow structure (hollow
resin particles and hollow silica). They may be used alone or in
combination of two or more.
[Binder Resin]
[0062] As a binder resin, vinyl resins are preferably included for
improving transfer property.
[0063] Other than vinyl resins, crystalline polyester resins and
amorphous polyester resins may be included as a binder resin.
<Vinyl Resin>
[0064] A resin formed by polymerization of one or more kinds of the
vinyl monomers, such as styrene monomers described below, can be
used as a vinyl resin.
(1) Styrene Monomers
[0065] Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,
.alpha.-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene,
p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene,
p-t-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene,
p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, and
derivatives of these monomers
(2) (Meth)acrylic Acid Ester Monomers
[0066] Methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl
(meth)acrylate, iso-propyl (meth)acrylate, iso-butyl
(meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl
(meth)acrylate, phenyl (meth)acrylate, diethylaminoethyl
(meth)acrylate and dimethylaminoethyl (meth)acrylate, and
derivatives of these monomers
(3) Vinyl Esters
[0067] Vinyl propionate, vinyl acetate, and vinyl benzoate
(4) Vinyl Ethers
[0068] Vinyl methyl ether and vinyl ethyl ether
(5) Vinyl Ketones
[0069] Vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl
ketone
(6) N-Vinyl Compounds
[0070] N-vinyl carbazole, N-vinyl indole, and N-vinyl
pyrrolidone
(7) Others
[0071] Vinyl compounds such as vinylnaphthalene and vinylpyridine;
acrylic acid or methacrylic acid derivatives such as acrylonitrile,
methacrylonitrile, and acrylamide
[0072] It is preferable to use vinyl monomers containing
ionic-dissociative group such as a carboxy group, a sulfonic acid
group or a phosphoric acid group. Specific examples are as
follows.
[0073] Examples of a monomer containing a carboxy group are:
acrylic acid, methacrylic acid, maleic acid, itaconic acid,
cinnamic acid, fumaric acid, monoalkyl maleate, and monoalkyl
itaconate. Examples of a monomer containing a sulfonic acid group
are: styrenesulfonic acid, allylsulfosuccinic acid, and
2-acrylamido-2-methylpropanesulfonic acid. An example of a monomer
containing a phosphoric acid group is acid phosphooxyethyl
methacrylate.
[0074] Furthermore, by using poly-functional vinyl compounds as
vinyl monomers, the vinyl polymer may be changed into a
cross-linked resin. Examples of a poly-functional vinyl compound
include: divinylbenzene, ethylene glycol dimethacrylate, ethylene
glycol diacrylate, diethylene glycol dimethacrylate, diethylene
glycol diacrylate, triethylene glycol dimethacrylate, triethylene
glycol diacrylate, neopentylglycol dimethacrylate, and
neopentylglycol diacrylate.
[0075] The vinyl resin may be prepared by polymerization through
any known polymerization technique, such as bulk polymerization,
solution polymerization, emulsion polymerization, miniemulsion
polymerization, or dispersion polymerization, and prepared by using
any polymerization initiator typically used in polymerization of
the above monomers can be used, for example, a peroxide,
persulfide, persulfate, or azo compound.
<Polyester Resin>
[0076] The polyester resin includes any known polyester resin
obtained by polycondensation reaction of a di- or more carboxylic
acid component (hereinafter, also simply referred to as
"polycarboxylic acid component") and a di- or more alcohol
component (hereinafter, also simply referred to as "polyalcohol
component").
(Polycarboxylic Acid)
[0077] Unsaturated aliphatic polycarboxylic acids, aromatic
polycarboxylic acids, and the derivatives thereof are preferably
used. As long as an amorphous resin can be formed, saturated
aliphatic polycarboxylic acids may also be used in combination.
Examples of unsaturated aliphatic polycarboxylic acids include
methylene succinic acid, fumaric acid, maleic acid, 3-hexenedioic
acid, 3-octenedioic acid, unsaturated aliphatic dicarboxylic acids
such as succinic acid substituted with an alkyl group of 1 to 20
carbon atoms or alkenyl group of 2 to 20 carbon atoms,
3-butene-1,2,3-tricarboxylic acid, 4-pentene-1,2,4-tricarboxylic
acid, unsaturated aliphatic tricarboxylic acids such as aconitic
acid, unsaturated aliphatic tetracarboxylic acids such as
4-pentene-1,2,3,4-tetracarboxylic acid, and the like. Further,
lower alkyl esters and anhydrides of these compounds can also be
used.
[0078] Specific examples of succinic acid that is substituted with
an alkyl group of 1 to 20 carbon atoms or an alkenyl group of 2 to
20 carbon atoms include dodecyl succinic acid, dodecenyl succinic
acid, octenyl succinic acid and the like. Further, lower alkyl
esters and anhydrides of these compounds can also be used. Examples
of aromatic polycarboxylic acids include aromatic dicarboxylic
acids such as phthalic acid, terephthalic acid, isophthalic acid,
t-butylisophthalic acid, tetrachlorophthalic acid, chlorophthalic
acid, nitrophthalic acid, p-phenylenediacetic acid,
2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid
andanthracene dicarboxylic acid; aromatic tricarboxylic acids such
as 1,2,4-benzenetricarboxylic acid (trimellitic acid),
1,2,5-benzenetricarboxylic acid (trimesic acid),
1,2,4-naphthalenetricarboxylic acid and hemimellitic acid; aromatic
tetracarboxylic acids such as pyromellitic acid and
1,2,3,4-butanetetracarboxylic acid; aromatic hexacarboxylic acids
such as mellitic acid, and the like. Further, lower alkyl esters
and anhydrides of these compounds can be used.
[0079] Examples of saturated aliphatic polycarboxylic acids are
desirably aliphatic dicarboxylic acids, particularly straight chain
carboxylic acids. Examples of such straight chain carboxylic acids
include oxalic acid, malonic acid, succinic acid, glutaric acid,
adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic
acid, 1,9-nonane dicarboxylic acid, 1,10-decane dicarboxylic acid,
1,11-undecane dicarboxylic acid, 1,12-dodecane dicarboxylic acid,
1,13-tridecane dicarboxylic acid, 1,14-tetradecane dicarboxylic
acid, 1,18-octadecane dicarboxylic acid, 1,20-eicosane dicarboxylic
acid, and the lower alkyl esters thereof and the anhydrides
thereof. They can be used alone or in combination of two or
more.
[0080] The number of carbon atoms of the dicarboxylic acids is not
particularly limited. However, from the viewpoint of easy
optimization of thermal properties, the number of carbon atoms is
preferably within the range of 1 to 20, more preferably within the
range of 2 to 15, particularly within the range of 3 to 12. The
dicarboxylic acid component is not limited to a single compound and
may be a mixture of two or more compounds.
[0081] The number of carbon atoms in the tri- or more carboxylic
acids is not particularly limited. However, in terms of ease of
optimization of the thermal properties, the number of carbon atoms
is preferably within the range of 3 to 20, more preferably within
the range of 5 to 15, particularly within the range of 6 to 12. The
polycarboxylic acid component is not limited to a single compound
and may be a mixture of two or more compounds.
(Polyalcohol)
[0082] In terms of the charge characteristic and the strength of
the toner, preferred polyalcohols that can be used in the present
invention are unsaturated aliphatic polyalcohols, aromatic
polyalcohols and the derivatives thereof. As long as the amorphous
polyester resin can be formed, saturated aliphatic alcohols may
also be used in combination.
[0083] Examples of unsaturated aliphatic polyalcohols include
unsaturated aliphatic diols such as 2-butene-1,4-diol,
3-butene-1,4-diol, 2-butyne-1,4-diol, 3-butyne-1,4-diol and
9-octadecene-7, 2-diol; glycerin, trimethylolpropane,
pentaerythritol, sorbitol and the like. Further, derivatives of
these compounds can also be used.
[0084] Examples of aromatic polyalcohols include bisphenols such as
bisphenol A and bisphenol F; alkylene oxide adducts of the
bisphenols such as ethylene oxide adducts and propylene oxide
adducts; 1,3,5-benzenetriol, 1,2,4-benzenetriol,
1,3,5-trihydroxymethylbenzene and the like. Further, derivatives of
these compounds can also be used. Among them, bisphenol A-based
compounds such as ethylene oxide adduct and propylene oxide adduct
of bisphenol A are preferably used in terms of particularly
improving the charge uniformity and ease of optimization of the
thermal properties of the toner.
[0085] The polyalcohol component is not limited to a single
compound and may be a mixture of two or more compounds. The number
of carbon atoms in tri- or more alcohols is not particularly
limited. However, in terms of ease of optimization of the thermal
properties, the number of carbon atoms are preferably from 3 to
20.
[0086] Here, an amorphous polyester resins is a polyester resin
having an amorphous property, which designates a property of
indicating a glass transition point (Tg) in an endothermic curve
obtained by measurement with differential scanning calorimetry
(DSC), but not indicating a clear endothermic peak of a melting
point during the temperature rising step. Here, "a clear
endothermic peak" designates an endothermic peak having a half
bandwidth within 15.degree. C. in an endothermic curve obtained
under the condition of a temperature raising rate of 10.degree.
C./min.
[0087] A crystalline polyester resin is a polyester resin having a
crystalline property. Here, "a crystalline property" designates a
property of indicating a clear endothermic peak of a melting point
during the temperature rising step in an endothermic curve obtained
by measurement with DSC.
[Releasing Agent]
[0088] Examples of releasing agents that can be used include
hydrocarbon waxes such as polyethylene wax, polypropylene wax,
polybutene wax and paraffin wax; silicones that exhibits a
softening point when heated; fatty acid amides such as oleic acid
amide, erucamide, ricinolic acid amide and stearic acid amide;
vegetable waxes such as carnauba wax, rice wax, candelilla wax,
wood wax and jojoba oil; animal waxes such as bee wax; ester waxes
such as fatty acid esters and montanic acid esters;
mineral/petroleum waxes such as montan wax, ozocerite, ceresin,
microcrystalline wax and Fischer-Tropsch wax; modified products of
thereof; and the like.
[0089] Among them, waxes with low melting point, specifically
within the range of 60.degree. C. to 85.degree. C., are preferably
used in terms of the releasability in low-temperature fixing. The
percentage of the releasing agent in toner base particles is
preferably within the range of 1 to 20 mass %, more preferably
within the range of 5 to 15 mass %.
[Charge Controlling Agent]
[0090] The toner particles according to the present invention may
include a charge controlling agent, if necessary. The charge
controlling agent is not particularly limited and any known
compound can be used.
[External Additive]
[0091] The white toner according to the present invention may
contain particles of an external additive.
[0092] External additive particles known in the art may be used.
Examples of such external additive particles include inorganic
oxide fine particles such as silica fine particles, alumina fine
particles and titania fine particles; inorganic stearate compound
fine particles such as aluminum stearate fine particles and zinc
stearate fine particles; inorganic titanate compound fine particles
such as strontium titanate and zinc titanate; and the like. They
may be used alone or in combination of two or more. It is preferred
that a gloss treatment with a silane coupling agent, a titanium
coupling agent, a higher fatty acid or a silicone oil is given to
these inorganic fine particles in order to improve the thermal
storage stability and the environmental stability.
[0093] Organic fine particles may also be used as external additive
particles. Organic fine particles that can be used are spherical
organic particles having a number average primary particle size of
approximately from 10 to 2000 nm. Specifically, organic fine
particles of homopolymers such as styrene and methylmethacrylate
and copolymers thereof can be used.
[0094] Lubricants may also be used as an external additive.
Lubricants are used for the purpose of improving the cleaning
property and the transferring property. Specific examples thereof
include metal salts of higher fatty acids such as stearates of
zinc, aluminum, copper, magnesium, calcium and the like, oleates of
zinc, manganese, iron, copper, magnesium and the like, palmitates
of zinc, copper, magnesium, calcium and the like, linoleates of
zinc, calcium and the like, ricinoleates of zinc, calcium and the
like, and the like.
[0095] These external additives may be used in a variety of
combinations.
[0096] The amount of external additive added is preferably within
the range of 0.1 to 10.0 parts by mass with respect to 100 parts by
mass of the toner particles. The external additive may be added by
using any of a variety of mixing machines known in the art such as
a turbuler mixer, a Henschel mixer, a nauta mixer or a V-shaped
mixer
[Particle Diameter of Toner Particle]
[0097] The volume-based median diameter of the toner particles
according to the present invention is preferably 3 .mu.m to 8
.mu.m, more preferably 5 .mu.m to 8 .mu.m. The median diameter can
be controlled in manufacturing by controlling the concentration of
aggregation agent, amount of added organic solvent, fusion time,
composition of the binder resin, and the like. The volume-based
median diameter within above range can faithfully reproduce an
extremely minute dot image of 1200 dpi.
[0098] The volume-based median diameter of the toner particles is
measured and calculated with a measuring device "MULTISIZER-3"
(Beckman Coulter Corp.) connected to a computer system with a data
processing software "Software V3.51". Specifically, 20 mL of
surfactant solution (for the purpose of dispersing toner particles,
e.g. neutral detergent containing a surfactant component, diluted
by 10 times with pure water) is added to 0.02 g of toner particles
and mixed. Thereafter, the solution is subjected to ultrasonic
dispersion for 1 minute so that toner particle dispersion is
prepared. By using a pipette, the toner particle dispersion is
added to "ISOTON II" (Beckman Coulter Corp.) in a beaker set in a
sample stand until the concentration displayed on the measuring
device reaches 8%. At this concentration, it is possible to obtain
a reproducible measurement value. The particle count and the
aperture diameter of the measuring device are respectively set to
25000 and 50 .mu.m. The measurement range of 1 .mu.m to 30 .mu.m is
divided into 256 sections, and the frequency values of the
respective sections are calculated. The volume-based median
diameter is defined as the particle diameter where the percentage
of cumulative volume of the larger particles reaches 50%.
(Average Circularity of Toner Particles)
[0099] In the toner of the present invention, it is preferred that
the average circularity of the toner particles of the toner is
within the range of 0.920 to 1.000, more preferably within the
range of 0.920 to 0.995 in terms of the stability of the charge
characteristic and the low-temperature fixability. When the average
circularity falls within this range, the individual toner particles
are less crushable. This prevents the triboelectric charging member
from smudges and stabilizes the charge characteristic of the
toners. Further, high quality images can be formed. The average
circularity of the toner particles is measured with an "FPIA-2100"
(Sysmex Corp.). Specifically, a measurement sample (toner
particles) is mixed with an aqueous solution containing a
surfactant and is further subjected to ultrasonic dispersion for 1
minute. Thereafter, photographs are taken with the "FPIA-2100"
(Sysmex Corp.) in the measurement conditions of the HPF (high power
photographing) mode at an adequate concentration corresponding to a
number of HPF detection of 3000 to 10000. The average circularity
of the toner is calculated by determining the circularity of
individual toner particles according to the following Equation and
dividing the sum of circularities of the individual toners by the
total number of toner particles. When the number of HPF detection
is within this range, the result is reproducible.
Circularity=(Circumference of circle having same area as projected
image of particle)/(Perimeter of projected image of particle)
<<Developing Agent for Electrostatic Charge Image
Development>>
[0100] The toner of the present invention may be used as a magnetic
or nonmagnetic one-component developer or as a two-component
developer by being mixed with a carrier. When used as a
two-component developer, examples of carriers that can be used
include magnetic particles known in the art that are made of metals
such as iron, ferrite and magnetite, alloys of these metals with
another metal such as aluminum and lead, and the like. Among them,
ferrite particles are preferably used. Further, carriers that can
also be used include coated carriers, in which the surface of
magnetic particles is covered with a coating agent such as a resin,
and dispersed carriers, in which magnetic fine powder is dispersed
in a binder resin.
[0101] It is preferred that the volume-based median diameter of the
carrier is preferably within the range of 15 .mu.m to 100 .mu.m,
more preferably within the range of 25 .mu.m to 60 .mu.m. The
volume-based median diameter of the carrier can be measured
typically with a laser diffraction particle size measuring device
"HELOS" (Sympatecs GmbH) equipped with a wet disperser.
<<Manufacturing Method of Electrostatic Charge Image
Developing White Toner>>
[0102] The manufacturing method of electrostatic charge image
developing white toner according to the present invention is not
particularly limited, but preferably includes a step of preparing a
dispersion liquid of the binder rein, a dispersion liquid of the
group Ga of rutile type titanium oxide particles, and a dispersion
liquid of the group Gb of rutile type titanium oxide particles and
a step of aggregating and fusing the binder resin, the group Ga of
rutile type titanium oxide particles, and the group Gb of rutile
type titanium oxide particles.
[0103] Hereinafter, an exemplary manufacturing method of toner
(toner particle) according to the present invention will be
described.
[Manufacturing Method of Toner Particle]
[0104] The toner particles used in the present invention includes
toner base particles including rutile type titanium oxide particles
as colorant and a binder resin.
[0105] The manufacturing method of the toner particles is not
particularly limited, and known manufacturing method can be used.
For example, the toner particles can be prepared by a method of
manufacturing grinded toner (grind method) through steps of
kneading, grinding, and classification and by a polymerization
method of manufacturing toner by forming particles through
polymerization of polymerizable monomers while controlling the
shape and size (for example, emulsion polymerization method, a
suspension polymerization method, and a polyester elongation
method). In particular, as described above, the manufacturing
method preferably includes a step of preparing a dispersion liquid
of the binder resin, a dispersion liquid of the group Ga of rutile
type titanium oxide particles, and a dispersion liquid of the group
Gb of rutile type titanium oxide particles and a step of
aggregating and fusing the binder resin, the group Ga of rutile
type titanium oxide particles, and the group Gb of rutile type
titanium oxide particles. It can be said that one of the effective
manufacturing method is an emulsion association method, which
includes a step of aggregating the resin particles having a
diameter of about 120 nm prepared by emulsion polymerization method
or a suspension polymerization method.
[0106] Hereinafter, an exemplary manufacturing method of toner
particles by an emulsion association method will be described. The
steps of emulsion association method to prepare toner particles are
summarized as follows:
(1) Step of preparing dispersion liquids (1-1) Step of preparing a
dispersion liquid of resin particles (1-2) Step of preparing a
dispersion liquid of colorant particles (2) Step of aggregating and
fusing resin particles (3) Aging step (4) Cooling step (5) Washing
step (6) Drying step (7) Step of treating with external additive
(according to necessity) Hereinafter, each step is described.
(1) Step of Preparing Dispersion Liquids
[0107] In the step of preparing dispersion liquids, a dispersion
liquid of the binder resin, a dispersion liquid of the group Ga of
rutile type titanium oxide particles, and a dispersion liquid of
the group Gb of rutile type titanium oxide particles are prepared.
This step preferably includes a step of preparing a dispersion
liquid of resin particles and a step of preparing a dispersion
liquid of colorant particles as follows.
(1-1) Step of Preparing a Dispersion Liquid of Resin Particles
[0108] In this step, polymerizable monomers are put into an aqueous
medium and polymerized to form binder resin particles (hereinafter
also simply referred to as "resin particles") having a diameter of
about 120 nm. Resin particles containing wax can be also formed.
Resin particles containing wax can be prepared by dissolving or
dispersing wax in the polymerizable monomers, followed by
polymerization in an aqueous medium.
(1-2) Step of Preparing a Dispersion Liquid of Colorant
Particles
[0109] Step of preparing a dispersion liquid of colorant particles
includes preparing dispersion liquids of colorant particles by
dispersing the group Ga of rutile type titanium oxide particles and
the group Gb of rutile type titanium oxide particles (hereinafter,
they are also collectively referred to as "colorant") into an
aqueous medium in the form of fine particles. For the purpose of
improving dispersion stability, a surfactant or a dispersion
stabilizer may be added.
[0110] The above-described dispersion of the colorant/releasing
agent can be performed by means of mechanical energy. The disperser
is not particularly limited, and examples of dispersers include
homogenizers, low-speed shearing dispersers, high-speed shearing
dispersers, friction dispersers, high-pressure jet dispersers,
ultrasonic dispersers, high-pressure impact dispersers (Altimizer),
emulsion dispersers, and the like.
[0111] Dispersion stabilizers known in the art can be used. For
example, dispersion stabilizers such as tricalcium phosphate are
soluble in acids or alkalis and preferably used. In terms of
environmental issues, enzymatically degradable dispersion
stabilizers are preferably used.
[0112] Examples of surfactants that can be used include anionic
surfactants, cationic surfactants, nonionic surfactants and
ampholytic surfactants known in the art. The dispersion diameter
can be measured, for example, by dynamic light scattering with a
"MICROTRAC UPA-150" (Nikkiso Co., Ltd.). The dispersion is
preferably performed until the dispersion diameter reaches the
primary diameter of the titanium oxide particle. It is determined
that the dispersion diameter have reached the primary diameter when
the dispersion diameter measured during dispersion by dynamic light
scattering becomes constant.
(2) Step of Aggregating and Fusing Resin Particles
[0113] In the step of aggregating and fusing resin particles, the
binder resin, the group Ga of rutile type titanium oxide particles,
and the group Gb of rutile type titanium oxide particles are
aggregated and fused.
[0114] More specifically, the step includes aggregating the resin
particles and colorant particles (rutile type titanium oxide
particles) in an aqueous medium, and obtaining particles by fusing
these aggregated particles. In this step, an aggregation agent such
as alkali metal salt or alkaline earth metal salt is added to the
aqueous medium, in which resin particles and colorant particles are
present. Subsequently, aggregation process is performed by heating
the dispersion at a temperature that is equal to or greater than
the glass transition point of the resin particles and equal to or
greater than the melting peak temperature (.degree. C.) of the
mixture. At the same time, process of fusing the resin particles
with each other is performed. Preferably, the resin particles and
the colorant particles prepared in the previous steps are added to
the reaction system and the aggregation agent such as magnesium
chloride is added thereto, so that particles are formed by
performing the aggregation process of the resin particles and the
colorant particles while the fusion process of the particles is
performed at the same time. When the particle size reaches the
target size, salts such as saline is added to stop aggregation.
(3) Aging Step
[0115] Subsequent to the above step of aggregating and fusing resin
particles, in the aging step, the reaction system is heated until
the particles are aged to have the desired average circularity.
(4) Cooling Step
[0116] In the cooling step, the dispersion liquid of the particles
is cooled at the cooling rate of 1 to 20.degree. C./min. The
cooling method is not particularly limited. For example, the
dispersion is cooled by circulating a coolant from the outside of
the reaction vessel, or by adding cold water directly to the
reaction system.
(5) Washing Step
[0117] The washing step includes the following steps; a
solid-liquid separation step to separate the particles from the
particle dispersion liquid cooled to a predetermined temperature in
the above cooling step; and a washing step to clean the
solid-liquid separated particles formed into a wet cake-like
assembly by removing adhered substances such as a surfactant and an
aggregation agent.
[0118] In the washing step, the particles are washed with water
until the electrical conductivity of the filtrate reaches a level
of 10 .mu.S/cm. The filtration method is not particularly limited,
and examples of methods include centrifugation, reduced pressure
filtration with a Nutsche, filtration with a filter press, and the
like.
(6) Drying Step
[0119] In the drying step, the washed particles are subjected to a
drying process to obtain dried particles. Dryers that can be used
in the drying step include dryers known in the art such as spray
dryers, vacuum freeze dryers, reduced pressure dryers, fixed rack
dryers, movable rack dryers, fluidized-bed dryers, rolling dryers
and stirring dryers, and the like.
[0120] The water content of the dried particles is preferably equal
to or less than 5 mass %, more preferably equal to or less than 2
mass %. When the dried particles are aggregated by weak
interparticle force, they may be subjected to a cracking process.
Cracking machines that can be used for this purpose include
mechanical cracking machines such as jet mills, Henschel mixers,
coffee mills and food processors.
(7) Step of Treating with External Additive
[0121] Toner particles are prepared by mixing the external additive
to the dried particles in the step. The external additive may be
added by using mechanical mixing machines such as a Henschel mixer
or a coffee mill.
[0122] The materials (binder resin, releasing agents, etc.) used
for preparing the above toner particles are described above.
<<Image Forming Apparatus>>
[0123] FIG. 2 is a schematic cross section diagram of an exemplary
image forming apparatus in which the toner according to the present
invention can be used. The image forming apparatus according to the
present invention includes a charger, an electrostatic charge image
former, a developer, a transferring unit, and a fixer. The
developer preferably forms a toner image by developing an
electrostatic charge image using a developing agent for
electrostatic charge image development including the electrostatic
charge image developing white toner according to the present
invention.
[0124] Furthermore, the image forming apparatus according to the
present invention preferably includes five or more electrostatic
charge image formers and five or more developers. Specifically, the
image forming apparatus preferably includes five electrostatic
charge image formers and five developers, respectively
corresponding to white, cyan, magenta, yellow, and black, for
example. A full color image can be thereby formed with white color
having hiding property, hue, and transfer property that comply with
the demand in the market of production printing.
[0125] The image forming apparatus 100 is a so-called tandem type
color image forming apparatus and includes five image forming units
10W, 10Y, 10M, 10C, and 10Bk, an endless belt intermediate
transferring unit 7, sheet feeding unit 21, and a fixer 24. A
document scanner SC is disposed above a body A of the image forming
apparatus 100.
[0126] The image forming unit 10W for forming a white image
includes a charger 2W, an exposing unit 3W, a developer 4W, a first
transferring roller 5W as a first transferring unit, and a cleaning
unit 6W, which are disposed around a drum photoreceptor 1W.
[0127] The image forming unit 10Y for forming a yellow image
includes a charger 2Y, an exposing unit 3Y, a developer 4Y, a first
transferring roller 5Y as a first transferring unit, and a cleaning
unit 6Y, which are disposed around a drum photoreceptor 1Y.
[0128] The image forming unit 10M for forming a magenta image
includes a charger 2M, an exposing unit 3M, a developer 4M, a first
transferring roller 5M as a first transferring unit, and a cleaning
unit 6M, which are disposed around a drum photoreceptor 1M.
[0129] The image forming unit 10C for forming a cyan image includes
a charger 2C, an exposing unit 3C, a developer 4C, a first
transferring roller 5C as a first transferring unit, and a cleaning
unit 6C, which are disposed around a drum photoreceptor 1C.
[0130] The image forming unit 10Bk for forming a magenta image
includes a charger 2Bk, an exposing unit 3Bk, a developer 4Bk, a
first transferring roller 5Bk as a first transferring unit, and a
cleaning unit 6Bk, which are disposed around a drum photoreceptor
1Bk.
[0131] The five image forming units 10W, 10Y, 10M, 10C, and 10Bk
respectively include the photoreceptors 1W, 1Y, 1M, 1C, and 1Bk at
the center, the charger 2W 2Y, 2M, 2C, and 2Bk, the exposing units
3W, 3Y, 3M, 3C, and 3Bk, the rotary developer 4W, 4Y, 4M, 4C, and
4Bk, and the cleaning units 6W, 6Y, 6M, 6C, and 6Bk for cleaning
the photoreceptors 1W, 1Y, 1M, 1C, and 1Bk.
[0132] The image forming units 10W, 10Y, 10M, 10C, and 10Bk have
the same configuration except for the colors of toner images formed
on the photoreceptors 1W, 1Y, 1M, 1C, and 1Bk. Thus, the following
description focuses on the image forming unit 10W.
[0133] The image forming unit 10W includes the charger 2W, the
exposing unit 3W, the developer 4W, and the cleaning unit 6W, which
are disposed around the photoreceptor 1W (image retainer). The
image forming unit 10W forms a white (W) toner image on the
photoreceptor 1W. In the present embodiment, at least the
photoreceptor 1W, the charger 2W, the developer 4W, and the
cleaning unit 6W are integrated in the image forming unit 10W.
[0134] The charger 2W applies a uniform potential to the
photoreceptor 1W. In the present invention, the charger is of, for
example, a contact or contactless roller charging type.
[0135] The exposing unit 3W exposes the photoreceptor 1W provided
with the uniform potential by the charger 2W in response to image
signals (white) to form an electrostatic latent image corresponding
to the white image. The exposure 3W includes light emitting
elements (LEDs) arrayed in the axial direction of the photoreceptor
1W and an imaging element, or includes a laser optical system.
[0136] The developer 4W is composed of a developing sleeve that
includes, for example, a built-in magnet and rotates while
retaining a developing agent, and a voltage-applying device that
applies a DC and/or AC bias voltage between the developing sleeve
and the photoreceptor. In particular, the developer 4W preferably
forms a toner image by developing an electrostatic charge image
using a developing agent for electrostatic charge image development
including the electrostatic charge image developing white toner
according to the present invention
[0137] The fixer 24 is of, for example, a heat roller fixing type
that is composed of a heating roller including a heat source
therein and a pressurizing roller disposed in a state being pressed
to the heating roller so as to form a fixing nip portion.
[0138] The cleaning unit 6W is composed of a cleaning blade and a
brush roller disposed upstream of the cleaning blade.
[0139] The aforementioned components, including the photoreceptor,
the developer, and the cleaning unit, may be integrated into a
processing cartridge (image forming unit) that is detachably
provided on the body of the image forming apparatus 100.
Alternatively, the photoreceptor and at least one of the charger,
the exposing unit, the developer, the transferring unit, and the
cleaning unit may be integrally supported to form a single
processing cartridge (image forming unit) that is detachably
provided on the apparatus body with a guiding unit, such as a rail
in the apparatus body.
[0140] The endless-belt intermediate transferring unit 7 includes
an endless intermediate transferring belt 70 (a semiconductive
endless belt as a second image retainer) wound around and rotatably
supported by multiple rollers.
[0141] The color images formed by the image forming units 10W, 10Y,
10M, 10C, and 10Bk are sequentially transferred onto the rotating
intermediate transferring belt 70 with the respective first
transferring rollers 5W, 5Y, 5M, 5C, and 5Bk (first transferring
units), to form a synthesized color image. A transfer medium P (an
image retainer to retain a fixed final image; e.g., a plain paper
or a transparent sheet) accommodated in a sheet feeding cassette 20
is fed by the sheet feeding unit 21, and is transported to a second
transferring roller 5b (second transferring unit) via multiple
intermediate rollers 22A, 22B, 22C, and 22D and register rollers
23. The color image on the intermediate transferring belt 70 is
transferred at once onto the transfer medium P in a second
transferring operation. The color image transferred on the transfer
medium P is fixed by the fixer 24. The transfer medium P is then
pinched between discharging rollers 25 and is conveyed to a sheet
receiving tray 26 provided outside of the apparatus. The image
retainers for retaining a toner image transferred from the
photoreceptor, such as the intermediate transferring belt and the
transfer medium, are collectively called transferring media.
[0142] After the transfer of the color image onto the transfer
medium P with the second transferring roller 5b (second
transferring unit) and the curvature separation of the transfer
medium P from the endless intermediate transferring belt 70, the
residual toner on the intermediate transferring belt 70 is removed
by the cleaning unit 6b.
[0143] The first transferring roller 5Bk abuts the photoreceptor
1Bk all the time during the image formation. The first transferring
rollers 5W, 5Y, 5M, and 5C abut the respective photoreceptors 1W,
1Y, 1M, and 1C only during the formation of a color image.
[0144] The second transferring roller 5b abuts the intermediate
transferring belt 70 only during passage of the transfer medium P
therebetween for the second transferring operation.
[0145] A housing 8 can be drawn along supporting rails 82L and 82R
from the apparatus body A.
[0146] The housing 8 accommodates the image forming units 10W, 10Y,
10M, 10C, and 10Bk, and the endless belt intermediate transferring
unit 7.
[0147] The image forming units 10W, 10Y, 10M, 10C, and 10Bk are
aligned in the vertical direction. The endless belt intermediate
transferring unit 7 is disposed on the left of the photoreceptors
1W, 1Y, 1M, 1C, and 1Bk in FIG. 2. The endless belt intermediate
transferring unit 7 includes the intermediate transferring belt 70
rotatably wound around rollers 71, 72, 73, and 74, the first
transferring rollers 5W, 5Y, 5M, 5C, and 5Bk, and the cleaning unit
6b.
[0148] Although the image forming apparatus 100 illustrated in FIG.
2 is a color laser printer, the photoreceptor of the present
invention can also be applied to monochrome laser printers and
copiers. The exposure light source may be a light source other than
a laser, such as an LED light source.
[0149] As described above, the image forming apparatus 100
according to the present invention includes five or more
electrostatic charge image formers and five or more developers. A
full color image can be thereby formed with white color having
excellent hiding property, hue, and transfer property that comply
with the demand in the market of production printing.
<<Image Forming Method>>
[0150] The image forming method includes a step of forming a latent
image, a developing step, a transfer step, and a fixing step. The
image forming method preferably uses the electrostatic charge image
developing white toner according to the present invention and an
electrostatic charge image developing colored toner including
colorant exhibiting a color other than white. An image having
hiding property, hue, and transfer property that comply with the
demand in the market of production printing can be thereby
provided.
[0151] The image forming method may further include a charging step
and a cleaning step.
[Electrostatic Charge Image Developing Colored Toner Including
Colorant Exhibiting a Color Other than White]
[0152] The electrostatic charge image developing colored toner
including colorant exhibiting a color other than white is not
particularly limited. Any known toner can be used, for example, a
toner including general colorant.
[Charging Step]
[0153] The photoreceptor (electrophotographic photoreceptor) is
charged in the charging step. A method for charging is not
particularly limited. For example, the above-described charger can
be preferably used.
[Step of Forming Latent Image]
[0154] In this step, an electrostatic latent image is formed on the
electrophotographic photoreceptor (a support of an electrostatic
latent image).
[0155] An electrophotographic photoreceptor is not particularly
limited. For example, a drum type photoreceptor composed of an
organic photoreceptor such as polysilane and phthalopolymethine may
be used.
[0156] The electrostatic latent image is formed by uniformly
charging the surface of the electrophotographic photoreceptor; and
then, exposing imagewise the surface of the electrophotographic
photoreceptor by the exposure.
[0157] The exposure is not particularly limited and the above
described exposure can be used.
[Developing Step]
[0158] In a developing step, the electrostatic latent image is
developed using a dry developing agent containing the toner
according to the present invention and a toner image is thereby
formed.
[0159] The toner image is formed, for example, in the above
developer using a dry developing agent containing the toner
according to the present invention.
[0160] Specifically, in the developer, the toner and the carrier
are stirred to be mixed. During that time, the toner is charged by
friction. The toner is retained on the surface of the rotating
magnet roller to form a magnetic brush. Since the magnet roller is
arranged in the vicinity of the electrophotographic photoreceptor,
a part of toner constituting the magnetic brush formed on the
surface of the magnet roller moves to the surface of the
photoreceptor by the electric attraction. As a result, the
electrostatic latent image is developed by the toner to form a
toner image on the surface of the photoreceptor.
[Transferring Step]
[0161] In this step, the toner image is transferred to an image
support.
[0162] The toner image is transferred to the image support by
peeling and charging the toner image to the image support.
[0163] Examples of transferring unit include a corona transferring
device with a corona discharge; a transfer belt; and a transfer
roller.
[0164] An intermediate transfer member may be used in the
transferring step as follows. For example, a toner image is
first-transferred to an intermediate transfer member, and then,
this toner image is secondly-transferred to an image support.
Otherwise, the toner image formed on the electrophotographic
photoreceptor may be directly transferred to the image support.
[0165] The image support is not particularly limited. Examples of
the image support include a various materials such as plain paper
from thin paper to thick paper, high quality paper, coated printing
paper such as art paper and coat paper, commercially available
Japanese paper and post card paper, plastic film for OHP, cloth,
and the like
[Fixing Step]
[0166] In the fixing step, the toner image transferred on the image
support is fixed on the image support. The fixing method is not
limited in particular but may be include the above known fixer, for
example, a heat roller fixing type composed of a heating roller
including a heat source therein and a pressurizing roller disposed
in a state being pressed to the heating roller so as to form a
fixing nip portion.
[Cleaning Step]
[0167] The liquid developing agent which is not used for image
formation is remained on a developing agent support member such as
the developing roller, the photoreceptor, and the intermediate
transfer member. In the cleaning step, the remained liquid
developing agent is removed from the developing agent support
member.
[0168] A cleaning method is not limited in particular. A preferable
method includes using a blade that rubs the surface of the
photoreceptor by locating at the position from which the edge
portion of the blade abuts the photoreceptor. For example, the
above-described cleaning units can be used.
[0169] The applicable embodiments of the present invention are not
limited to the embodiments described-above. They may be suitably
changed within the scope of not exceeding the object of the present
invention.
EXAMPLES
[0170] Hereinafter, specific examples of the present invention will
be described by referring to specific examples, but the present
invention is not limited thereto. In the examples, the description
of "parts" or "%" represents "mass parts" or "mass %" unless
specific notice is given.
[Manufacturing Method of Rutile Type Titanium Oxide Particles T-1
to T-13]
[0171] Hereinafter, manufacturing method of rutile type titanium
oxide particles T-1 to T-13 is described. Unless otherwise noted, a
"group of rutile type titanium oxide" and "rutile type titanium
oxide particles" are not distinguished from each other and they are
collectively referred to as "rutile type titanium oxide particles"
through the following description.
<Manufacturing Method of Rutile Type Titanium Oxide Particles
T-1>
[0172] Ilmenite ores including 55 mass % of TiO.sub.2 was used as a
starting material. After drying at 150.degree. C. for 2 hours,
sulfuric acid was added to dissolve the material to obtain an
aqueous solution of TiOSO.sub.4. The aqueous solution of
TiOSO.sub.4 was concentrated and of a titania sol (6.0 parts by
mass) including rutile crystal was added as crystal nuclei. After
hydrolysis at 130.degree. C., slurry of TiO(OH).sub.2 including
impurities was obtained. The slurry was washed with water
repeatedly at pH 5 to 6 (solution temperature: 25.degree. C.) to
remove sulfuric acid, FeSO.sub.4, and the impurities. A
meta-titanic acid (TiO(OH).sub.2) slurry of high purity was thereby
obtained. The slurry was filtered, calcined at 180.degree. C. for
10 hours, and crushed with a jet mill until there is no aggregation
of fine particles. Rutile type titanium oxide fine particles having
a volume average primary particle diameter (hereinafter, also
simply referred to as "average diameter") of 233 nm was thereby
obtained. (The diameters at the peak top position were the same as
the volume average primary particle diameters in rutile type
titanium oxide particles T-1 to T-13 and anatase type titanium
oxide particles T-14.)
<Step of Dispersing Rutile Type Titanium Oxide Particles
T-1>
[0173] Rutile type titanium oxide particles T-1 (210 parts by mass)
was placed into an aqueous solution of a surfactant (sodium alkyl
diphenyl ether disulfonate (1 mass %) in deionized water (482 parts
by mass)) and was dispersed with a beads mill (beads diameter: 0.1
mm) to prepare a dispersion liquid T-1A of white colorant fine
particles, in which white colorant fine particles are dispersed in
an aqueous medium. The solid content was adjusted to 30 mass %.
[0174] Dispersion treatment was performed until the dispersion
diameter measured by dynamic light scattering becomes constant. The
average dispersion diameter was 233 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-2>
[0175] Rutile type titanium oxide particles T-2 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (2.5 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 105 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 105 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-3>
[0176] Rutile type titanium oxide particles T-3 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (11.5 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 430 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 430 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-4>
[0177] Rutile type titanium oxide particles T-4 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (8.0 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 304 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 304 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-5>
[0178] Rutile type titanium oxide particles T-5 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (7.6 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 295 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 295 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-6>
[0179] Rutile type titanium oxide particles T-6 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (6.4 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 255 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 255 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-7>
[0180] Rutile type titanium oxide particles T-7 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (2.3 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 96 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 96 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-8>
[0181] Rutile type titanium oxide particles T-8 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (12.0 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 450 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 450 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-9>
[0182] Rutile type titanium oxide particles T-9 were prepared as in
the rutile type titanium oxide particles T-1, except that a titania
sol (4.5 parts by mass) including rutile crystal was added as
crystal nuclei. Rutile type titanium oxide fine particles having an
average diameter of 180 nm was thereby obtained. As in the rutile
type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 180 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-10>
[0183] Rutile type titanium oxide particles T-10 were prepared as
in the rutile type titanium oxide particles T-1, except that a
titania sol (13.0 parts by mass) including rutile crystal was added
as crystal nuclei. Rutile type titanium oxide fine particles having
an average diameter of 500 nm was thereby obtained. As in the
rutile type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 500 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-11>
[0184] Rutile type titanium oxide particles T-11 were prepared as
in the rutile type titanium oxide particles T-1, except that a
titania sol (3.2 parts by mass) including rutile crystal was added
as crystal nuclei. Rutile type titanium oxide fine particles having
an average diameter of 130 nm was thereby obtained. As in the
rutile type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 130 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-12>
[0185] Rutile type titanium oxide particles T-12 were prepared as
in the rutile type titanium oxide particles T-1, except that a
titania sol (4.1 parts by mass) including rutile crystal was added
as crystal nuclei. Rutile type titanium oxide fine particles having
an average diameter of 163 nm was thereby obtained. As in the
rutile type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 163 nm.
<Step of Manufacturing and Dispersing Rutile Type Titanium Oxide
Particles T-13>
[0186] Rutile type titanium oxide particles T-13 were prepared as
in the rutile type titanium oxide particles T-1, except that a
titania sol (13.6 parts by mass) including rutile crystal was added
as crystal nuclei. Rutile type titanium oxide fine particles having
an average diameter of 522 am was thereby obtained. As in the
rutile type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 522 nm.
[Step of Manufacturing and Dispersing Anatase Type Titanium Oxide
Particles T-14]
[0187] Anatase type titanium oxide particles T-14 were prepared as
in the rutile type titanium oxide particles T-1, except that a
titania sol (6.0 parts by mass) including anatase crystal was added
as crystal nuclei. Rutile type titanium oxide fine particles having
an average diameter of 233 nm was thereby obtained. As in the
rutile type titanium oxide particles T-1, dispersion treatment was
performed until the dispersion diameter reaches the primary
diameter of the titanium oxide particle diameter. The average
dispersion diameter was 233 nm.
<Measurement Method of Volume Average Primary Particle Diameter
of Titanium Oxide Fine Particles>
[0188] For each of the groups of rutile type titanium oxide
particles T-1 to T-13 and anatase type titanium oxide particles
T-14, a volume particle size distribution curve was prepared on the
basis of the primary diameter of randomly-selected 100 particles
measured with a transmission type electron microscope "JEM-2000FX"
(manufactured by JEOL). The particle diameter and the volume ratio
were represented on a horizontal axis and on a vertical axis,
respectively. The diameter of the peak-lop position of the volume
particle size distribution curve was determined as the diameter of
the peak-top position of the groups of rutile type titanium oxide
particles T-1 to T-13 and anatase type titanium oxide particles
T-14.
[0189] The conditions of accelerating voltage etc. were as
follows.
Accelerating voltage: 80 kV, Magnification: 50000 times
<Measurement Method of Volume Average Particle Diameter of
Titanium Oxide Dispersion Liquid>
[0190] The volume average particle diameter of the titanium oxide
fine particles in the dispersion liquid was measured with a
particle size distribution measuring device ("NANOTRAC UPA-EX 150"
manufactured by NIKKISO CO., LTD). The value of d50 was determined
as an average particle diameter.
[Preparation of Toner 1 to 17]
<Manufacturing of Toner 1>
(Preparation of Resin-Particle Dispersion Liquid A)
(1) First Polymerization
[0191] An surfactant solution of sodium n-dodecylsulfate (8 parts
by mass) dissolved in deionized water (3000 parts by mass) was
prepared in a reaction vessel equipped with a stirrer, a
temperature sensor, a cooling tube, and a nitrogen inlet, and the
reactor was heated to an inner temperature of 80.degree. C. while
the solution was stirred under a nitrogen stream at a stirring rate
of 230 rpm. After heating, a solution of potassium persulfate (KPS)
(10 parts by mass) dissolved in deionized water (200 parts by mass)
was added to the above surfactant solution, and the internal
temperature was controlled to be 80.degree. C. Subsequently, a
mixed solution of polymerizable monomers including the following
compounds was added dropwise over one hour:
TABLE-US-00001 Styrene 480 parts by mass n-butyl acrylate 250 parts
by mass Methacrylic acid 68 parts by mass
n-octyl-3-mercaptopropionate 16 parts by mass
[0192] After completion of the addition, the system was heated at
80.degree. C. for two hours with stirring to perform polymerization
(first polymerization). A "resin-particle dispersion liquid 1h"
including "resin particles 1h" was thereby prepared.
(2) Second Polymerization
[0193] The following monomers and paraffin wax were placed into a
flask equipped with a stirrer, and the wax was dissolved by heating
to 90.degree. C. to prepare a monomer solution.
[0194] Meanwhile, a surfactant solution including sodium
polyoxyethylene-2-dodecyl ether sulfate (7 parts by mass) dissolved
in deionized water (800 parts by mass) was heated to 98.degree. C.
The "resin particles 1h" (260 parts by mass in terms of solid
content) and the mixed solution of monomers were added to the
surfactant solution.
TABLE-US-00002 Styrene 45 parts by mass n-butyl acrylate 120 parts
by mass n-octyl-3-mercaptopropionate 1.5 parts by mass Paraffin wax
"HNP-51 (Nippon Seiro Co., Ltd.)" 67 parts by mass
[0195] Subsequently, a dispersion liquid including emulsified
particles was prepared by mixing and dispersing treatment for one
hour with a mechanical dispersing machine "Cleamix" (made by M
Technique Co., Ltd.) having a circulating path.
[0196] Subsequently, a solution including potassium persulfate (6
parts by mass) dissolved in deionized water (200 parts by mass) was
added to the dispersion. The system was heated at 82.degree. C. for
one hour with stirring to perform polymerization (second
polymerization). A "resin-particle dispersion liquid 1HM" including
"resin particles 1HM" was thereby prepared.
(3) Third Polymerization
[0197] An initiator aqueous solution of potassium persulfate (11
parts by mass) in deionized water (400 parts by mass) was added to
the above "resin-particle dispersion liquid 1HM". After heating to
80.degree. C., a mixed solution of polymerizable monomers including
the following compounds was added dropwise over one hour:
TABLE-US-00003 Styrene 435 parts by mass n-butyl acrylate 130 parts
by mass Methacrylic acid 33 parts by mass
n-octyl-3-mercaptopropionate 8 parts by mass
[0198] After completion of the addition, the solution was stirred
with heating for two hours to perform polymerization (third
polymerization). Subsequently, the solution was cooled to
28.degree. C. to prepare "resin-particle dispersion liquid A". The
volume-based median diameter of the particles measured with an
electrophoretic light scattering photometer "ELS-800 (manufactured
by Otsuka Electronics Co., Ltd.)" was 150 nm. The glass transition
point measured by a known method was 45.degree. C. The
weight-average molecular weight of the resin was 32000.
(4) Preparation of "Toner Base Particles 1"
[0199] The following components were placed into a flask equipped
with a stirrer, a temperature sensor, a cooling tube, and a
nitrogen inlet.
TABLE-US-00004 Resin-particle dispersion liquid A 300 parts by mass
(in terms of solid content) Deionized water 1400 parts by mass
Dispersion liquid of rutile type titanium 8.4 parts by mass (in
oxide particles T-1 terms of solid content) Dispersion liquid of
rutile type titanium 75.6 parts by mass (in oxide particles T-4
terms of solid content)
[0200] Furthermore, a solution including sodium
polyoxyethylene-2-dodecyl sulfate (3 parts by mass) dissolved in
deionized water (120 parts by mass) was added, the temperature of
the mixture was adjusted to 30.degree. C. A 5 mol/L aqueous sodium
hydroxide solution was then added to the reactor to adjust the pH
of the mixture to 10.
[0201] Subsequently, a solution of magnesium chloride hexahydrate
(35 parts by mass) dissolved in deionized water (35 parts by mass)
was added to the mixture with agitation at 30.degree. C. over 10
minutes. The system was left to stand for three minutes, and then
was heated over 60 minutes to 90.degree. C. While the system was
kept at 90.degree. C., the aggregation and fusion of the particles
was performed. In this state, the diameters of the particles
growing in the reaction vessel were measured with "Multisizer 3"
(made by Beckman Coulter, Inc.) When the volume-based median
diameter reached 6.5 .mu.m, an aqueous solution of sodium chloride
(150 parts by mass) dissolved in deionized water (600 parts by
mass) was added to terminate the growth of the particles. The
system was further heated at 98.degree. C. under stirring as an
aging process to fuse the particles until the average circularity
measured with an analyzer "FPIA-2100" (made by Sysmex Corporation)
reached 0.965.
[0202] Next, the solution was cooled to 30.degree. C., pH was
adjusted to 2 using hydrochloric acid, and stirring was
stopped.
[0203] The dispersion liquid of toner base particles prepared
through the above steps was subjected to solid liquid separation
with a basket type centrifugal separator "MARK III" (MODEL NUMBER
60.times.40) (manufactured by MATSUMOTO KIKAI MFG. CO., LTD.) to
extract a "wet cake of the toner base particles".
[0204] The wet cake was washed with the basket type centrifugal
separator using deionized water (45.degree. C.) until the
electrical conductivity of the filtrate reaches a level of 5
.mu.S/cm. Subsequently, the wet cake was moved to an airflow type
dryer "FLASH JET DRYER" (manufactured by SEISHIN ENTERPRISE CO.,
LTD.), and the drying process of the wet cake was performed until
the water quantity thereof became 0.5 mass %. White "toner base
particles 1" was thereby prepared.
(Preparation of Toner 1)
[0205] Silica (number average primary diameter: 30 nm, 2.0 parts by
mass) treated with n-butyltrimethoxysilane was added to the toner
base particles 1 (100 parts by mass) using Henschel mixer "FM10B"
(NIPPON COKE & ENGINEERING CO., LTD.) for 20 minutes at 60
m/second of peripheral speed of agitation impeller, at 30.degree.
C. to add an external additive. After adding an external additive,
coarse particles were removed using a sieve having an open
mesh-size of 90 .mu.m to prepare "Toner 1" with the above external
additive.
<Manufacturing of Toners 2 to 8 and 10 to 17>
[0206] Toners 2 to 8 and 10 to 17 were prepared as in the
manufacturing of Toner 1, except that the mass and the mass ratio
of the two groups (Ga and Gb) of rutile type titanium oxide
particles having different volume particle size distribution were
changed as described in TABLE 1. The toner base particles have a
constitution of resins similar to that of Toner 1.
TABLE-US-00005 TABLE 1 Titanium oxide particle Toner Ga Gb Db - Da
Mass of Ga:Mass Mass % to Manufacturing No. No. Da [nm] No. Db [nm]
[nm] of Gb binder resin Toner resin method of toner Remarks 1 T-1
233 T-4 304 71 10:90 28 Vinyl resin Polymerization Present
invention 2 T-2 105 T-9 180 75 10:90 28 Vinyl resin Polymerization
Present invention 3 T-3 430 T-10 500 70 10:90 28 Vinyl resin
Polymerization Present invention 4 T-2 105 T-11 130 25 10:90 28
Vinyl resin Polymerization Present invention 5 T-4 304 T-10 500 196
10:90 28 Vinyl resin Polymerization Present invention 6 T-1 233 T-4
304 71 30:70 28 Vinyl resin Polymerization Present invention 7 T-1
233 T-4 304 71 5:95 28 Vinyl resin Polymerization Present invention
8 T-1 233 T-4 304 71 10:90 15 Vinyl resin Polymerization Present
invention 9 T-1 233 T-4 304 71 10:90 65 Polyester resin
Pulverization Present invention 10 T-4 304 -- -- 0 -- 28 Vinyl
resin Polymerization Comparative example 11 T-1 233 T-4 304 71 2:98
28 Vinyl resin Polymerization Comparative example 12 T-1 233 T-4
304 71 40:60 28 Vinyl resin Polymerization Comparative example 13
T-5 295 T-4 304 9 10:90 28 Vinyl resin Polymerization Comparative
example 14 T-6 255 T-10 500 245 10:90 28 Vinyl resin Polymerization
Comparative example 15 T-7 96 T-12 163 67 10:90 28 Vinyl resin
Polymerization Comparative example 16 T-8 450 T-13 522 72 10:90 28
Vinyl resin Polymerization Comparative example 17 T-14 233 T-4 304
71 10:90 28 Vinyl resin Polymerization Comparative example
(Anatase) Vinyl resin Polymerization Comparative example
<Manufacturing of Toner 9>
(Synthesis of Amorphous Polyester Resin)
[0207] Terephthalic acid (TPA) (90 parts by mass), trimellitic acid
(TMA) (6 parts by mass), fumaric acid (FA) (19 parts by mass),
dodecenylsuccinic acid anhydride (DDSA) (85 parts by mass),
Bisphenol A propylene oxide adduct (BPA.cndot.PO) (351 parts by
mass), and Bisphenol A ethylene oxide adduct (BPA.cndot.EO) (58
parts by mass) were placed in a reaction vessel equipped with an
agitator, a thermometer, a condenser and a nitrogen gas inlet, and
the reaction vessel was purged with dried nitrogen gas. Titanium
tetrabutoxide (0.1 parts by mass) was added, and the reaction
system was stirred for 8 hours at 180.degree. C. under a nitrogen
gas stream for polymerization reaction. Titanium tetrabutoxide (0.2
parts by mass) was further added and the reaction system was
stirred for 6 hours at 220.degree. C. The reaction vessel was
depressurized to 10 mmHg and the reaction was continued under the
reduced pressure to prepare amorphous polyester resin having a
weight-average molecular weight (Mw) of 17000.
[0208] Subsequently, the following components were kneaded at
120.degree. C. in a biaxial extruder. After the kneading, the
mixture was cooled to 25.degree. C.
TABLE-US-00006 Amorphous resin 290 parts by mass Fischer-Tropsch
wax "FNP-0090" (releasing 10 parts by mass agent) Rutile type
titanium oxide particles T-1 8.4 parts by mass Dispersion liquid of
rutile type titanium oxide 75.6 parts by mass particles T-4
[0209] The mixture was preliminarily pulverized with a hammer mill,
was roughly pulverized with a turbo mill (Freund-Turbo
Corporation), and further finish-pulverized with an air classifier
utilizing the Coanda effect. Toner 9 with a volume median diameter
of 7.0 .mu.m was thereby prepared.
[Preparation of Developing Agents 1 to 17 for Toners 1 to 17]
[0210] Developing agents 1 to 17 were prepared by mixing each of
the toners 1 to 17 and a ferrite carrier such that a toner
concentration became 5% by mass. The ferrite carrier was coated
with a silicone resin and a volume average particle diameter
thereof was 35 .mu.m.
[Evaluation]
[0211] A commercial printer "bizhub PRESS C1070" (manufactured by
KONICA MINOLTA, INC.), was used as a machine to output an image for
evaluation. OHP film was used as medium on which the image for
evaluation was formed. The image for the following evaluation was a
solid image having a toner density of 4.0 g/m.sup.2 (patch image of
4.0 cm.times.2.5 cm).
[0212] The evaluation result is shown in TABLE 2.
<Evaluation of Whiteness (Hiding Power)>
[0213] The color of the output image was measured with
spectrophotometer "X-Rite 939" (manufactured by X-Rite, Inc.) in a
CIE 1976 (L*A*B*) color system. The whiteness (hiding power) was
evaluated from the obtained L* value in the CIE 1976 (L*A*B*) color
system on the basis of the following criteria.
[0214] A: L* value is 95 or more
[0215] B: L* value is 80 or more and less than 95
[0216] C: L* value is less than 80
<Evaluation of Hue>
[0217] From the above-described image, saturation was calculated by
the following equation and used as hue.
Hue(C*)={(a*).sup.2+(b*).sup.2}.sup.0.5
(Evaluation Standard)
[0218] A: C* is 0 or more and less than 1.0
[0219] B: C* is 1.0 or more and less than 1.5
[0220] C: C* is more than 1.5
<Evaluation of Transfer Property>
[0221] The mass of toner on a developed photoreceptor and the mass
of toner transferred on an intermediate transfer medium were
evaluated. Transfer rate was calculated by the following
equation.
Transfer rate (%)={(mass of toner transferred on intermediate
transfer medium)/(mass of toner on developed
photoreceptor)}.times.100
[0222] A: Transfer rate is 90% or more
[0223] B: Transfer rate is 80% or more and less than 90%
[0224] C: Transfer rate is less than 80%
TABLE-US-00007 TABLE 2 Toner Whiteness Hue Transfer rate No. L'
value Evaluation C' Evaluation [%] Evaluation Remarks 1 95 A 0.3 A
92 A Present invention 2 84 B 0.2 A 90 A Present invention 3 85 B
1.3 B 84 B Present invention 4 81 B 0.4 A 90 A Present invention 5
82 B 1.3 B 84 B Present invention 6 88 B 0.4 A 90 A Present
invention 7 90 A 1.4 B 89 B Present invention 8 80 B 0.2 A 97 A
Present invention 9 98 A 0.9 A 80 B Present invention 10 68 C 1.9 C
82 B Comparative example 11 72 C 1.7 C 78 C Comparative example 12
71 C 1.2 B 80 B Comparative example 13 77 C 1.8 C 83 B Comparative
example 14 70 C 1.4 B 75 C Comparative example 15 60 C 0.4 A 89 B
Comparative example 16 64 C 2.1 C 70 C Comparative example 17 59 C
0.3 A 95 A Comparative example
(Summary)
[0225] It is clear from the above results that the present
invention provides an electrostatic charge image developing white
toner and the like, having hiding property, hue, and
transferability complying with the demand in the market of
production printing.
[0226] Although embodiments of the present invention have been
described and illustrated in detail, it is clearly understood that
the same is by way of illustration and example only and not
limitation, the scope of the present invention should be
interpreted by terms of the appended claims.
* * * * *